Binge drinking, defined as men consuming five or more drinks and women drinking four or more drinks in 2 hours, is a serious problem in the United States. According to the Centers for Disease Control and Prevention (CDC), around 90 percent of alcohol consumed among minors is in the form of binge drinking.

Adolescent binge drinking poses a number of dangers. Obviously, heavy drinking can lead people to engage in high-risk behaviors, and teenagers tend to be more likely than adults to take reckless risks. Scientists have also long been concerned that the still-developing teenage brain is more vulnerable to damage from alcohol than a fully mature adult brain.

Past research has linked heavy alcohol use among teenagers to changes in myelin – the protective coating surrounding nerve fibers that boosts communication between neurons – and cognitive impairment later in life. Recent studies have also documented deficits in memory and cognition among teens who binge drink compared to those who don’t.

But according to study co-author Dr. Heather Richardson, PhD, of the University of Massachusetts Amherst, it has been unclear whether such brain changes are a direct result of alcohol consumption or other factors.

With a view to finding out, Dr. Richardson and colleagues assessed the effects of alcohol consumption on the brains of male adolescent rats. For 2 weeks, one group of rats had access to sweetened alcohol each day, while the other group – acting as controls – had access to sweetened water.

The researchers explain that, like teenagers, rats have a preference for sweet beverages and were happy to work for their drink by pressing a lever that granted access to it. This triggered high levels of voluntary alcohol consumption among the rats, similar to that of adolescent binge drinking in humans.

At the end of the study period, the researchers analyzed the brains of the rats, focusing on their levels of myelin.

They found that the rats that drank the sweetened alcohol every day for 2 weeks had reduced myelin in the prefrontal cortex of the brain — a region of the brain crucial for decision making and the regulation of emotions — compared with the rats that drank the sweetened water.

When assessing myelin levels in the rats’ brains months later – when they had reached adulthood – they found the rats that had consumed the sweetened alcohol during adolescence continued to show reduced myelin levels in the prefrontal cortex.

“Our study provides novel data demonstrating that alcohol drinking early in adolescence causes lasting myelin deficits in the prefrontal cortex,” says Dr. Richardson. “These findings suggest that alcohol may negatively affect brain development in humans and have long-term consequences on areas of the brain that are important for controlling impulses and making decisions.”

Furthermore, the researchers note that when the rats that consumed alcohol during adolescence were exposed to alcohol again in adulthood, the effects on the brain were comparable in each instance, even though the rats consumed less alcohol for shorter durations during adolescence. The researchers say this indicates that in teenage years, the brain may have heightened sensitivity to alcohol.

The effects of teenage binge drinking on memory

In another experiment, both groups of rats were subject to a working memory task as adults, which tested their ability to retain new information for short periods.

The adult rats that had consumed alcohol during adolescence displayed a poorer performance on this task, compared with the adult rats that drank the sweetened water during adolescence.

Dr. Richardson and colleagues say their findings indicate that as well as causing lasting structural damage to the brain, binge drinking during adolescence may impair cognitive functions associated with learning and memory later in life.

The team says they hope their findings will pave the way for new strategies to treat alcohol use disorders. In addition, they say that “results from this work focusing on the prefrontal cortex could also help us better understand the function of myelin and how myelin deficits may contribute to other psychiatric conditions associated with prefrontal impairments, such as impulsivity, Tourette syndrome and schizophrenia.”